Spring brake cylinder with an emergency release device

ABSTRACT

The invention relates to a spring brake cylinder with an emergency release device, comprising the following: a housing in which a spring-loaded piston can be moved axially with a piston rod, at least one spring-loaded spring, wherein the emergency release device comprises an actuation device, an emergency release mechanism to interrupt the power transmission between the spring-loaded piston and the piston rod and a holding device for holding the emergency release device in a transmission condition. The invention further includes a blocking device to prevent the holding device from holding of the emergency release mechanism in a transmission position when the spring-loaded piston only partly released

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a pneumatically, hydraulically orelectromechanically operated spring brake cylinder with an emergencyrelease device. The brake cylinder includes a housing, in which aspring-loaded piston is axially displaceable by a piston rod, at leastone spring-loaded spring, and, in the case of pneumatic or hydraulicoperation, a pressure connection for admitting pressure fluid to thespring-loaded piston. The emergency release device includes an operatingdevice and an emergency release mechanism for interrupting thetransmission of force between the spring-loaded piston and the pistonrod with a holding device for holding the emergency release device in atransmission condition.

From German Patent Documents DE PS 26 08 502, corresponding to U.S. Pat.No. 4,063,491, and DE PS 27 48 540, corresponding to U.S. Pat. No.4,226,168, brake cylinders are known with emergency release devices forthe interruption and the automatic return of the braking function of aspring-loaded cylinder, in which case, the emergency release lever forthe emergency release must be operated or held until the accumulatedspring force is completely reduced.

Although these solutions have been successful per se, when the operatingor emergency release lever is not operated or held sufficiently long, atextremely low temperatures, conditions of the spring accumulator areconceivable which result only in a partial force reduction. Because ofthe viscosity of the lubricants, which increases with the fallingtemperature, the time period until the force is completely reduced islengthened in comparison to higher temperatures. During this timeperiod, the emergency release lever would therefore have to remainoperated or held in order to completely reduce the accumulated springforce.

Here, the invention uses a different approach. The invention starts withthe recognition of the present problems and, in view of these problems,has the object of further developing the spring brake cylinder of theabove-mentioned type such that situations are reliably avoided in whichonly a partial reduction or build-up of force takes place.

The invention solves this task. The holding device for holding theemergency release device at different holding positions is supplementedby a blocking device for preventing the holding of the holding devicewhen the spring-loaded piston is only partially released. This preventsa holding, particularly an engaging of the emergency release operationwhen the spring accumulator is only partially released. Thus, for theemergency release of the spring accumulator, a one-time brief operationof the emergency release lever will be sufficient because the prematureengaging of the blocking mechanism is reliably prevented by the blockingdevice.

According to one embodiment of the invention, the blocking devicecomprises a locking bar which locks the emergency release mechanism ofthe spring accumulator in the released position until the springaccumulator is completely released or is operative again.

In a cost-effective constructively simple further development, theholding device has a detent pawl acting upon a gear wheel. However, itis also conceivable that the holding device is designed to be rotatingand/or linear and/or locking and/or clamping and permits several holdingpositions. A spring in the transmission of force of the operation of theemergency release device in a simple manner prevents intermediateconditions of the detent pawl.

According to various embodiments of the invention, particularly thefollowing locking bar arrangements are useful:

between the spring-loaded housing and the spring-loaded piston, or

between the piston rod and the spring-loaded piston, or

between the piston rod and the spring-loaded housing.

Additional advantageous further developments of the invention arecontained herein.

In the following, essentially two different basic embodiments of theinvention and the blocking devices implemented within the scope of theinvention will be described in detail with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a brake cylinder, according to thepresent invention, taken along lines AA of FIG. 2.

FIG. 2a is a cross-sectional view of a brake cylinder, according to thepresent invention, taken along lines BB of FIG. 1.

FIG. 2b is a side view of a detent pawl of FIG. 2a.

FIG. 2c is a cross-sectional view of the detent pawl taken along linesCC of FIG. 2b.

FIGS. 3a and 3 b show the spring-loaded cylinder released by pressure.

FIGS. 4a and 4 b show the spring actuator in the braking position andstart of the emergency release operation.

FIGS. 5a and 5 b show emergency release operation and detent pawllocked.

FIGS. 6a and 6 b show the spring actuator emergency-released and theemergency release operation withdrawn.

FIG. 7 shows a second embodiment of a brake cylinder with an emergencyrelease device, according to the present invention, similar to that ofFIG. 1.

FIG. 8a shows a cross-sectional view of a third embodiment of a brakecylinder with emergency release device incorporating the principles ofthe present invention.

FIG. 8b shows an enlarged portion of FIG. 8a.

FIG. 9 is an end view of the embodiment of FIG. 8.

FIGS. 10a and 10 b are perspective views of the third embodiment of theemergency release device.

FIG. 11 shows another embodiment similar to that of FIG. 8 with amodified lock and bar arrangement.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First, by means of an example of embodiment one with reference to FIGS.1 and 2, the function of the spring accumulator of the first embodimentof the invention will be described.

FIGS. 1 and 2 show two different views of a spring-loaded cylinder 2having a housing 4 in which a spring-loaded piston 6 is arranged in anaxially displaceable manner and on whose outer circumference sealingdevices and sliding bands 8 a-8 c are distributed. The spring-loadedsprings 14, 16 are arranged between the spring-loaded piston 6 and anaxial housing cover 10 which is fastened on the inner circumference ofthe housing 4 by a snap ring 12.

Between the spring-loaded piston 6 and the housing 4, a pressure space18 is constructed which can be acted upon by pressure by an airconnection 20 in the circumference of the housing 4. The spring brakecan be released and applied by the venting and bleeding by way of theair connection 20. When the spring accumulator 4 is not in the emergencyreleased operating condition, the force of the spring-loaded springs 14,16 is supported by way of the spring-loaded piston 6 and either thepressure in the pressure space or volume 18 or a piston rod 24 on thespring loaded piston 6 on the braking device which is otherwise notshown here.

For releasing the engaged spring brake also without compressed air, thespring-loaded cylinder 6 has an emergency release device 26 whichpermits an interruption of the transmission of force between thespring-loaded piston 6 and the piston rod 24.

In the illustrated example, the emergency release device 26 or theemergency release mechanism portion of 26 is essentially based on thefunction of a spindle arrangement 28 with a detent pawl 30 which isswivellably disposed between two mutually axially offset sections 10 aand 10 b of the housing cover 10. A threaded spindle 32 of the spindlearrangement transmits force between the spring-loaded piston 6 and thepiston rod 24. The resulting torque of the spindle arrangement istransmitted in the blocked or transmission condition by a displaceableguide 34 having an adjusting spring 36 to a gear wheel 38, which can beblocked or released by the detent pawl 30 (see particularly also FIGS. 2and 5). For this purpose, one end of the detent pawl 30 engages in thegear wheel 38 in one of the operating positions of the emergency releasedevice. In contrast, the other end of the detent pawl 30 can be liftedout of the toothing of the gear wheel 38 by an emergency operating unitwith a Bowden cable 42 and a restoring spring 44 constructed at theBowden cable and a pressure spring 46. The rotation of the gear wheel 38is released in this position of the detent pawl 30. As a result, thetransmission of force between the spring-loaded piston 6 and the pistonrod 24 can be interrupted. The detent pawl 30 can be swivelled about anaxis 31. A catch spring 33 presses one end of the detent pawl 30 in thedirection of the toothing of the gear wheel 38.

When the emergency release device is operated when a braking or springforce is applied to the piston rod 24, a rotation of the threadedspindle 32 will be caused when the braking force is reduced so that thespring-loaded piston 6 impacts on the housing 4. In order to preventanother locking of the detent pawl 30 during the release operation, alocking bar 48 is arranged on the interior surface of section 10 b ofthe spring accumulator cover or housing cover 10, which locking bar 48holds back the lifted-out detent pawl 30.

The locking bar 48 essentially has a bolt-type shape and, on its endfacing the housing cover section 10 b, is equipped with a locking head51. Between the two-part housing cover 10 a, 10 b (which has anindentation in this area) and the locking head 51 (with an axialrecess), a locking spring 49 is arranged which presses the locking bar48 in the direction of the detent pawl 30. In one of the operatingpositions, the locking head 51 engages in a lateral stepped recess 35 ofthe detent pawl 30 for receiving the locking bolt 48 and locks thedetent pawl 30 in its release position (see FIG. 5b). The section of thelocking bar 48 facing away from the locking head 51 has a bolt-typeconstruction penetrating the interior housing cover section 10 a. Whenthe spring-loaded piston 6 is displaced in the direction of the housingcover 10, it compresses the locking bar spring 49 and presses thelocking head 51 of locking bar 48 out of its engaged position in thedent pawl 30 (FIGS. 1 and 2). Thus, only when the spring-loaded piston6, after a release operation, is again in the operative position, willthe locking bar 48 release the detent pawl again for an engagement.

The optional display device 54 illustrated in FIG. 2 shows the“emergency-released” condition of the spring-loaded cylinder 2, in whichthe display device 54 is contacted by the detent pawl 30, as shown inFIGS. 5 and 6a.

Essentially, the following different positions of the spring accumulatorare obtained before and after an emergency release operation: (Sequence:Operative—emergency releasing—operative)

1. Spring-Loaded Cylinder 2 Released by Pressure (FIG. 3):

The spring-loaded cylinder 2 is released by the pressure in the pressurevolume 18, and the spring-loaded piston is displaced in the direction ofthe housing cover 10. No braking force is applied to the piston rod 24,and the detent pawl 30 and the gear wheel 38 are in the lockedcondition.

2. Spring-Accumulator in the Braking Position, Start of the EmergenceRelease Operation (FIG. 4):

The spring-loaded cylinder 2 is in its braking position. The pressurevolume or the pressure space 18 is without pressure. The force of thespring-loaded springs 14, 16 is applied to the piston rod 24.

The emergency release operation is initiated by a pulling on theemergency release operation device. By way of the pressure spring 46 andthe driving device 40, the detent pawl 30 is lifted out of the toothingof the gear wheel 38.

3. Emergency Release Operation, Detent Pawl 30 Locked (FIG. 5):

The spring-loaded springs 14, 16 are supported by the spring-loadedpiston 6 on the spring-loaded housing cover 10. The piston rod 24 isfree of force, and it was moved into its starting position by the backpressure spring 50.

By means of the engaged locking head 51 of locking bar 48, the detentpawl 30 is held in its release position, and the display device 54 isactive.

4. Spring Accumulator Emergency-Released, Emergency Release OperationWithdrawn (FIG. 6):

The spring-loaded cylinder is in the “emergency-released” condition, andthe detent pawl 30 is locked. The emergency release operation device ordriver 40 was moved into the starting position by the restoring spring44.

5. Spring Accumulator Which Is Operative Again (FIG. 3):

The applying of pressure into the pressure volume 18 leads to therestoration of the readiness condition of the spring accumulator 2. Thelocking bar 48 holds the detent pawl 30 in the released condition untilthe spring-loaded springs 14, 16 again have their prestress and thespring-loaded piston 6 takes up its right end position, as illustratedin FIG. 3. The piston 6 moves the locking bar 48 to the right and thelocking head 51 out of engagement with the detent pawl 30. After theengagement of the detent pawl 30 and gear wheel 38, the tensionalconnection between the spring-loaded piston 6 and the piston rod 24 isrestored.

In order to ensure the engaging of the locking bar 31 in the detent pawl30 during an operation of the emergency release device, the pressurespring 46 is provided in the transmission of force between the emergencyrelease device and the driving device 40. The prestressing of thepressure spring 46 ensures the swivelling movement of the pawl 30 fromthe initial travel of unlocking of the gear wheel 38 to the furthertravel to the locking by the locking bar 48.

FIG. 7 shows a modification of the embodiment of FIGS. 1 to 6. In thisembodiment, a free running device of the gear wheel 38, here, a coneclutch 52, is constructed in the transmission of force between thespring-loaded piston 6 and the piston rod 24. The cone clutch 52 permitsa reduction of the shock occurring during the emergency releaseoperation because it ensures an unhindered continued running of the gearwheel 38 and of the threaded spindle 32 after the emergency releaseoperation.

In the first embodiment of FIGS. 1 to 6 and the modification of thisembodiment according to FIG. 7, the detent pawl 30 and its lockingdevice 48 are situated in the springloaded or housing cover 10 which isfixedly connected with the spring-loaded housing 4. The locking bar 48is operated by the spring-loaded piston. The pawl 30 itself is arrangedbetween two sections 10 a and 10 b of the housing cover 10 which can beassembled.

The embodiment of FIGS. 8, 9 and 10 basically differs from theembodiment of FIG. 1 as a result of the arrangement of the detent pawl30 and of the locking bar 48. The detent pawl 30 and the pertaininglocking bar 48 are arranged on the piston rod 24. The locking bar 48 ismoved by the threaded spindle 58 which is rotatable relative to thespringloaded piston 24.

The second embodiment of FIGS. 8, 9 and 10 therefore shows anotherpossibility of the locking bar arrangement. In this embodiment, thedetent pawl 30 is rotatably arranged on the piston rod 34 by a bolt (inthis regard, see the bore 30′ in the pawl 30; see FIGS. 10a, 10 b) andis operated by the spring-loaded piston 6. In this embodiment, thespring-loaded piston 6 and the spring-loaded spring 14 are arranged suchthat the pressure space 18 is situated on the right-hand side of thespring-loaded piston 6 in the drawing. The spring-loaded piston 6 isdisposed on the threaded spindle 58 which, at one of its ends, iffixedly screwed to the spring-loaded piston 6. In its area facing awayfrom the piston 6, the spindle 58 is provided with a type of trapezoidalthread. In the area of the trapezoidal thread, the threaded spindle 58is screwed into a sleeve 62 provided with a corresponding internalthread. The sleeve 62 is provided with an external toothing at its endfacing away from the springloaded piston 6, so that the gear wheel 38′is constructed in this area of the sleeve 62. In one of its operatingpositions, the detent pawl 30, which is arranged on an end area of theaxially and radially displaceable holding plate 56, engages in the gearwheel 38′ and blocks it. An operation of the emergency release devicedisplaces the plate 56 radially and releases the pawl 30 from the gearwheel 38′ and thereby interrupts the transmission of force between thespring-loaded piston 6 and the piston rod 24. In this case, the lockingbar 48—pushed forward by the locking bar spring 49′—engages in anopening of the holding plate 56 and locks it radially. The locking bar48 is moved and released by the spindle 58 fixedly connected with thespring-loaded piston 6.

In this embodiment of the invention, the locking bar 48 is thereforearranged between the piston rod 24 and the spring-loaded piston 6. Thelocking bar spring 49′ is disposed between the piston rod 24 and thespring-loaded piston 6. The holding plate 56 is radially displaceable inan interior cylindrical attachment 63 of the brake cylinder housing andmoves axially with the piston rod 24 and the spring-loaded piston 6. Theradial displacement of the plate 56 takes place by a coil spring 64which is supported on a bolt 65 in the holding plate 56 and on a holdingpart 66 which, in an immobile manner, is screwed to the piston rod 24 bya bolt 68.

As an alternative, a locking bar operation is conceivable between thepiston rod 24 and the spring-loaded housing 4. Such an embodiment isillustrated in FIG. 11. The basic construction of this embodiment issimilar to the embodiment of FIGS. 8 to 10 with respect to the couplingof the spring-loaded piston 6. However, the locking bar 48 isconstructed such that it impacts during the moving of the piston rod 24from the spring-loaded housing 4 and, during a continued movement, isrotated about an axis 47. This rotating movement and a reverse rotatingmovement by the spring 49 between the piston rod 6 and the locking bar48 move the locking bar 48 into its two operating positions and, in thismanner, move it into and out of the recess 64 of the holding plate 56.

Although the present invention has been described and illustrated indetail, it is to be clearly understood that this is done by way ofillustration and example only and is not to be taken by way oflimitation. The spirit and scope of the present invention are to belimited only by the terms of the appended claims.

What is claimed is:
 1. A spring brake cylinder with an emergency releasedevice comprising: a housing, in which a spring-loaded piston is axiallydisplaceable and a piston rod; at least one spring-loaded spring actingon the piston; the emergency release device including an operatingdevice and an emergency release mechanism for interrupting thetransmission of force between the spring-loaded piston and the pistonrod, the emergency release mechanism having a holding device for holdingthe emergency release device in a transmission condition, the holdingdevice having different positions; a blocking device for preventing theholding device from holding the emergency release mechanism in atransmission position while the spring-loaded piston is only partiallyreleased; and the blocking device having a locking bar which locks theholding device in a released position of the holding device until thespring-loaded piston is completely released.
 2. The spring brakecylinder according to claim 1, wherein the holding device is designed tobe one of rotating, linear, and clamping and to permit severalpositions.
 3. The spring brake cylinder according to claim 1, whereinthe holding device has a detent pawl acting upon a gear wheel.
 4. Thespring brake cylinder according to claim 3, including at least onespring in the transmission of force of the emergency release device foravoiding intermediate conditions of the detent pawl.
 5. The spring brakecylinder according to claim 3, wherein the detent pawl is on a holdingplate which is radially displaceable in the cylinder housing such thatradial displacement of the holding plate and of the detent pawl releasesor blocks the gear wheel.
 6. The spring brake cylinder according toclaim 5, wherein the locking bar is on the piston rod and is designed,in an operating position, to engage a recess of the holding plate andradially lock the holding plate.
 7. The spring brake cylinder accordingto claim 5, wherein the locking bar is swivellably disposed on thepiston rod such that, during axial movements of the piston rod, thelocking bar swivels from the cylinder housing into and out of a recessof the holding plate.
 8. The spring brake cylinder according to claim 3,wherein the transmission of force between the spring-loaded piston andthe piston rod includes a threaded spindle.
 9. The spring brake cylinderaccording to claim 8, wherein the torque of the threaded spindle istransmitted by a displaceable guide with an adjusting spring to the gearwheel which can be locked by the detent pawl.
 10. The spring brakecylinder according to claim 3, wherein the operating unit has a drivingdevice for driving the detent pawl, a Bowden cable and at least onerestoring spring and a pressure spring on the Bowden cable.
 11. Thespring brake cylinder according to claim 3, wherein the transmission offorce between the spring-loaded piston and the piston rod includes afree running device for the gear wheel.
 12. The spring brake cylinderaccording to claim 11, wherein the free running device is constructed asa cone clutch.
 13. The spring brake cylinder according to claim 3,wherein the locking bar can be displaced by the spring-loaded pistonfrom its locking position in the detent pawl.
 14. The spring brakecylinder according to claim 3, wherein the detent pawl and the lockingbar are on the piston rod.
 15. The spring brake cylinder according toclaim 1, wherein the locking bar is arranged in one of: between thehousing and the spring-loaded piston, between the piston rod and thespring-loaded piston, and between the piston rod and the housing. 16.The spring brake cylinder according to claim 1, wherein the force of thespring-loaded spring is supported either by the spring-loaded piston onthe pressure space or by the piston rod on the spring-loaded piston. 17.The spring brake cylinder according to claim 1, wherein the locking baris operated by a threaded spindle connected with the spring-loadedpiston.
 18. The spring brake cylinder according to claim 1, including adisplay device for displaying the operating condition of the emergencyrelease device.
 19. The spring brake cylinder according to claim 1,wherein the locking bar is essentially bolt-shaped and, at its endfacing a housing cover section, is equipped with a locking bar headwhich is designed for engaging in a recess of a detent pawl of theholding device.
 20. The spring brake cylinder according to claim 1,wherein a locking bar spring is arranged between a housing cover and thelocking bar, which locking bar spring presses the locking bar in thedirection of a detent pawl of the holding device.